Synthetic ester base lubricating composition containing a copper or cobalt acetylacetonate



United States Patent SYNTHETIC ESTER BASE LUBRICATING COM- POSITIONCONTAINING A COPPER OR CO- BALT ACETYLACETONATE Arthur W. Godfrey,Fishkill, N.Y., assignor to Texaco Inc., New York, N.Y., a corporationof Delaware No Drawing. Filed Dec. 13, 1966, Ser. No. 601,336 5 Claims.(Cl. 25242.7)

ABSTRACT OF THE DISCLOSURE A synthetic lubricating oil composition forturbine engines is disclosed comprising a synthetic base oil and a metalbis(trifluoroacetylacetonate) from the class consisting of copper (II)and cobalt (II) in an amount ranging from 0.01 to 1.0 weight percentbased on the weight of the lubricating oil composition.

This invention relates to a lubricating composition designed for thelubrication of turbine engines which operate over a wide temperaturerange and under severe operating conditions. More particularly, thisinvention relates to a synthetic lubricating oil composition having gooddeposit-inhibiting and oxidation resisting properties.

Synthetic base lubricants have been found to be useful for thelubrication of modern high performance turboprop, turbojet and turbofanengines. However, even these superior base oils must be modified to meetthe stringent performance requirements set by .the military and bycommercial aircraft engine manufacturers. It is particularly difficultto achieve a synthetic oil composition having all the properties towithstand extreme thermal and oxidative stress without laying downdeposits and becoming corrosive due to excessive oxidation of componentsof the synthetic oil.

Various additives and additive combinations have been employed toformulate synthetic lubricating oil compositions. Unfortunately, many ofthe compounded synthetic lubricating oils tend to promote corrosion ofvital metal components of turbine engines, do not sufiiciently inhibitoxidation of the synthetic oil base, or have an unsatisfactory level ofdeposit laydown and/or load-carrying properties. Deposit laydown andcorrosiveness have been particularly severe problems withhalogen-containing additives. A synthetic lubricating oil compositionhas now been discovered which has superior oxidation resistance anddeposit inhibiting properties while retaining an effective high level orover-all lubricating properties.

The lubricating composition of this invention broadly comprises asynthetic base fluad having lubricating properties containing a metalderivative of bis(trifluoroacetylacetonate). More specifically, theadditive is a metal bis- (trifluoroacetylacetonate) from the class ofmetals consisting of copper (II) and cobalt (II). The additive isemployed in an amount ranging from about 0.01 to 1 weight percent basedon the Weight of the lubricating oil composition, the preferredconcentration being from 0.05 to 0.3 weight percent. In a preferred formof this invention, the synthetic lubricating oil composition alsocontains a hydrocarbyl amine antioxidant to further enhance theextremely low deposit laydown of the lubricating oil composition.

The function of the particular bis(trifluoroacetylacetomates) of thisinvention appears to be unique. Metal acetylacetonates, in general, havebeen unsatisfactory in lubricating oil compositions because of theformation of and deposition of solids from the oils. Likewise, the useof fluorine-containing additives in lubricating oils has producedcompositions having unacceptable high levels of corrosion. Theproperties of bis(trifluoroacetylacetonate) "ice copper (III) and cobalt(11) appear to be unique even within the class of metaltrifluoroacetylacetonates in that they impart good oxidation resistanceand deposit laydown properties.

Synthetic ester-type base synthetic fluids are preferred for thelubricating composition of the invention. The base can be an aliphaticdiester of an organic dicarboxylic acid. The dicarboxylic acid componentis usually an aliphatic dicarboxylic acid containing 6 to 12 carbonatoms although glutaric acid esters and succinic acid esters can also beused. From the standpoint of cost and availability, the dibasic acids,adipic acid, sebacic acid and azelaic acid are favored. The aliphaticalcohols used to form the diesters usually contain at least 4 carbonatoms and may contain 20 or more carbon atoms, with C to C alcoholsbeing preferred.

Specific examples of the dialkyl esters of aliphatic dicarboxylic acidsare as follows: di-isooctyl azelate, di- 2-ethylhexyl sebacate,di-Z-ethylhexyl azelate, di-Z-ethylhexyl adipate, dilauryl azelate,di-sec-amyl-sebacate, di- Z-ethylhexyl alkenylsuccinate, di-Z-ethoxyethyl sebacate, di-2-(2'-methoxyethoxy) ethyl sebacate,di-2(2'-butoxyethoxy) ethyl alkenylsuccinate, etc.

In addition the aliphatic dicarboxylic acid esters described above,polyesters and complex ester lubricants formed by a reaction of analiphatic dicarboxylic acid, a glycol and a monofunctional compoundwhich is either an aliphatic monohydroxy alcohol or an aliphaticmonocarboxylic acid in specified mole ratios are also employed as asynthetic lubricating base in the composition of this invention.Polyesters of this type are described in US. 2,628,974. Complex estersby reaction of a mixture containing specified amounts of2-ethyl-l,3-hexane-diol, sebacic acid and 2-ethyl hexanol, and byreaction of a mixture containing adipic acid, diethylene glycol and2-ethylhexanoic acid illustrate this class of synthetic polyesterlubricating base.

Esters formed by the reaction of a monocarboxylic acid and a glycol orpolyol may also be used as the ester components. The acid component isusually an aliphatic acid containing 3 to 20 carbon atoms and preferaly4 to 10 carbon atoms. The glycol or polyol component is advantageously astraight glycol, such as 1,5-hexane diol, but ether glycols, such astetraethylene glycol may also be used. Sterically hindered neopentyltype glycols, such as Z-methyl, Z-ethyl, 1,3-propanediol, are favoredfor enhanced thermal stability.

Specific examples of the diesters of glycols are the following:di-n-decanoate of 1,4-butanediol, di-Z-ethylhexanote of 1,6-hexanediol,dilaurate of 1,4-hexanediol, dioctanoate of 1,5-pentanediol. Examples oftriesters are trimethyl propane triheptanoate and trioctanoate. Examplesof tctraesters are pentaerythritol tetracaproate and pentaerythritolesters with mixtures of aliphatic acids generally containing from threeto ten carbon atoms.

Complex esters formed by reacting trimethylol and tetramethylol alkaneswith various mole ratios of dibasic acids and monobasic acids oralcohols are other examples of polyesters useful for the base fluid ofthe lubricants of this invention. Pent-aerythritol tetraesters of Caliphatic carboxylic acids are a preferred class of polyesterlubricating oils. Polyphenyl ethers are also suitable for thelubricating oil base.

The optional antioxidant component for enhancing the deposit formingproperties of the lubricating oil of the invention comprises an aromaticamine having the formula:

3 4 in which R is an alkyl radical having from 1 to 8 carbon gradepentaerythritol esterified with a mixture of 38% atoms, R is hydrogen oran alkyl radical having from 1 valeric, 13% Z-methylpentanoic, 32%octanoic and 17 to 6 carbon atoms and R" is hydrogen, or a phenyl,pelargonic acid. This base fluid had the following propernaphthyl,aminophenyl or an .alkyl-substituted phenyl ties: radical in which thealkyl radical has from 1 to 8 carbon atoms. Examples of theseantioxidants include p-p'-di- Viscosity, cs. at 210 F 4.93 octyldiphenylamine, N-phenyl-l-naphthylamine, N- Viscosity, cs. at 100 F 25.6phenyl-p-phenylene diamine, N-N'-diphenyl-p-phenylene Viscosity, cs. at-40 F. 7023 diamine, N,N-bis(octylphenyl)-p-phenylene diamine, p-Viscosity index 131 hydroxy-diphenylamine,N-phenyl-N-isopropyl-p-phenyl- 10 Flash, F. 490 ene diamine, andN,N'-dioctyl-p-phenylene diamine. The

amines are employed in amounts ranging from 0.1 to The syntheticlubricating oil of the invention was preabout 5 percent by weight of thelubricant composition pared by mixing the additive into the base oil.The properwith the preferred amount being from about 0.5 to 3 ties ofthe lubricating oils of the invention and of the percent. base oil aregiven in Table I below:

TABLE 1 Base Oil+0.1% Base Oil+0.1% bis(trifluoro- Base 0il+0.1% BaseOi1+0.1% Base Oi1+0.1%

bis(trifluoroacetyltris(trifluorobis(trifiuorobis(trifluoro- Base Oilacetylaeetonate) acetylaeetylacctylaceacetonate) Cu(II) 1% p,paeetonate)acetonate) tonate) Co(II) Cu(II) deoctyldi- Fe(III) Mgul) phenylamine450 F. Antioxidant Test: Percent Vis. increase:

24 hours 700 77.6 505 438 48 hours 326 4, 000 Total Acid No.1

24 hours. 6. 5 3. 0

48 hours 19. 4 5. 5 600 F. Oil Mist Test, g. deposit/1,000 g. oil 13.90.8 0.1 27. 5 s. s 3. 2(590 F.)

1 Semi-solid.

2 Solid.

Other additive components can be advantageously in- The foregoing datashow that the lubricating oil of the corporated in the lubricantcomposition of the invention. invention was greatly improved inessential lubricating For example, it is conventional to add smallconcentraand deposit forming properties while oil compositions contionsof methacrylate polymers to improve dispersancy. taining similaradditives were substantially degraded or An anti-foam agent, such as ahydrocarbon or kerosene rendered totally ineffective. concentrate ofdimethyl silicone in an amount ranging Obviously, many modifications andvariations of the. from about 0.0001 to 0.01 percent by weight, isgenerally invention, as hereinbefore set forth, may be made withadded tothe lubricating oil. Detergents, such as the metal out departing fromthe spirit and scope thereof, and theresalts of phenates and sulfonates,are also used to advanfore only such limitations should be imposed asare inditage. In particular, barium sulfonates have been found cated inthe appended claims. useful since they inhibit corrosion and rusting. Iclaim:

The oxidation-corrosion resistance and deposit forming 1. A syntheticlubricating oil composition comprising properties of the lubricatingoils of the invention were a major portion of a synthetic ester basehaving lubricatdetermined in the following tests. ing properties anddeposit and oxidation reducing amounts The 450 F. Antioxidant Test isconducted in accordof a metal bis(trifiuoroacetylacetonate) additive,said ance with method 5308.4 of Federal Test Method Standmetal beingselected from the class consisting of copper ard No. 791a (issued Dec.31, 1961) except for certain (II) and cobalt (II). modifications toconform to Pratt and Whitney Aircraft 2. A lubricating oil according toclaim 1 containing Specification 521-B (Type II). The bath temperatureis from 0.01 to 1 weight percent of said metal bis(trifiuoromaintainedat 450 F.i1 F., instead of at 250 F. This acetylacetonate).

test was run for 48 hours with determination of viscosity 3. Alubricating oil according to claim 1 in which said increase and totalacid number taken at 24 hours and 48 additive isbis(trifluoroacetylacetonate) copper (II).

hours. 4. A lubricating oil according to claim 1 in which said The OilMist Test was described in a paper presented at synthetic oil base is anester base lubricating oil.

the ASLE/ASME Lubrication Conference in Minneapolis, 5. A lubricatingoil according to claim 4 in which said Minn., Oct. 18-20, 1966 byBartholomaei, Massey and synthetic oil base is an ester pentaerythritol.Holstedt. This test is conducted by passing a mist of oil through aglass tube containing a steel liner (shim stock) References Citedthrough the entire length of the tube. The tube is main- UNITED STATESPATENTS tamed at 600 F. while the 011 mlst 1s contlnuously passedthrough over a period of 16 hours. At the end of the 2323932 12/1940Tfwvne test period, the steel liner is removed, solvent washed and2,305,627 12/1942 LmFoln at 252-427 X weighed. The amount of tenaciousmaterial adhering to i g g -gth liner i det rm'ned and 's re orted as as f d 0c e s e 1 1 p gr m Q G 3,360,467 12/1967 McHugh et a1. 2s2 74posit per one thousand grams of oil put through the system. This testrepresents the formation of breather tube deposits in a jet engineDANIEL E. WYMAN, Primary Examiner.

The base oil employed in the tests below was technical W. H. CANNON,Assistant Examiner.

